[Somatosensory Evoked Potential during Cardiac Surgery]

Neurologic complications are common in cardiac surgery. The rate of complication can range from 1.6% to 23% for permanent neurologic deficits and from 7% to 61% for transient neurologic deficits. Although several studies have suggested the effectiveness of brain monitoring in reducing postoperative adverse neurologic outcomes, brain monitoring during cardiac surgery has not yet been adopted for routine use. Somatosensory evoked potential (SEP) can provide direct information on the integrity of somatosensory pathway such as SEP elicited by median nerve stimulation in cardiac surgery. An electrode is placed over primary sensory cortex, C3' C4', so called Shagss point. The N20/P25 waveform can be recorded. N20/P25 evoked potentials reflect the perfusion of medial brain circulation. When cerebral blood flow decreases or when brachial plexus is obstructed, N20/P25 amplitude decreases with latency delay. SEP can quickly detect brain ischemia and brachial plexus dysfunction, and it is useful for nervous system monitoring in cardiac surgery.